I just checked Magpul's website and it states that the Mossberg forend is now shipping. I checked Midway and Brownell's. They do not have them in stock yet, but soon I hope. Per Magpul you will need an 11 slot rail to mount an Afg.
I ordered one today from Midway. They are also on ebay already. But I did read on ebay that the forend can't be used with a heatshield. I will have to find out when mine arrives in a couple of days. Magpul and Midway's site do not say anything about not fitting with a heatshield. I did email magpul about this. Will see what they have to say. Will report back on these things when I know more.
They DO NOT work with the heat shields. The forend will have to be modified.. I was reading this on another site where a magpul employee was confirming it.
I may have to check and see what Midway's return policy is. It just makes me mad when it states that this is a direct replacement for the 590 and 590A1. I have the 590A1 but most of the 590's I have seen come with a heatshield.